This application is being filed with an appendix of computer program listings.
1. Field of the Invention
The present invention relates to a system for positioning a work point.
There are many industrial tasks that require the positioning of a human worker or a tool or machine well above or below ground level. For example, in nuclear power plants, radioactive contamination may adhere to the reactor cavity walls during refueling operations. This contamination can become airborne when the reactor cavity walls are left to dry, thus contaminating the entire building. To prevent this, reactor cavity walls must be quickly cleaned before the drying can occur.
The cleaning process can involve abrasive scrubbing, application of superheated pressurized water followed by vacuuming, high pressure blasting or application of a strippable coating which binds the contamination. In any of these decontamination processes, a human worker and/or a tool or working machine must be positioned at a point near the reactor wall to begin the cleaning operation, and must be moved up, down and across the cavity wall so that the entire structure may be cleaned completely. Because the reactor cavity wall is tall, the positioning and movement required to carry out the work is cumbersome, costly and often dangerous.
Typically, the worker or machine is deployed through the use of a crane positioned above a reactor cavity. A cleaning machine may be affixed to the arm of the crane, which then positions the machine at a point in the x-y plane adjacent the wall. Alternatively, a human worker having the necessary cleaning equipment enters a basket at the end of the crane arm, and is moved from place to place along the wall to effect manual cleaning. In either case, the crane is generally deployed from above the reactor cavity. This deployment is undesirable, since the use of these cranes is vital for other tasks, and their unavailability to support reactor cavity decontamination can extend the length of the refueling outage. This is a very costly situation.
Many other industrial applications require a similar positioning of a human worker, tool or machine. Fossil boilers, storage tanks for commodities such as water and conventional fuels, shipyards, dams and bridges, commercial and industrial buildings, skyscrapers, hangars, silos and towers all have a tall vertical surface that may need to be fully traversed to effect cleaning, painting, maintenance, repair or construction operations. The painting of these structures presents similar problems. As is the case with the nuclear reactor, it is often undesirable or impossible to deploy a crane on the roof or ground abutting the vertical surface. In addition to the need for being able to position the worker, tool or working machine over a wide area, the path over which the work point travels and the velocity and acceleration at which it travels are of critical importance, since all points in the plane must be traversed at a controlled velocity in order to ensure a complete and uniform application of paint. Accordingly, there is a great need for a system that can position a work point while controlling these motion parameters.